The chemical structure of glycerol phenylbutyrate, which helps clear nitrogen from the system before it can be converted to ammonia. Children’ s Colorado’ s Metabolic Service used it to treat a baby born with OTC deficiency disorder and was a site in the clinical trials.
A few days later, the baby transitioned to a drug called glycerol phenylbutyrate, which accomplishes the same thing but can be taken by mouth. The Metabolic Service was involved in clinical trials for it, before it was approved by the FDA in 2013.
Therapy continued after birth with tight monitoring from Children’ s Colorado’ s Level IV Neonatal Intensive Care Unit, and the baby has been there since. The NICU and Metabolic teams check his blood ammonia constantly and adjust medications and the precise amount of protein in his diet to maximize growth and minimize ammonia production. He’ s now three months old and awaiting a liver transplant.
“ We keep an eagle eye on him,” Dr. McCandless says.“ If there’ s even a hint his ammonia levels are rising we treat it aggressively. Every time this baby is fussy he gets his ammonia checked.”
The good news is that the transplanted liver will contain the enzyme needed to convert ammonia. It will essentially be curative.
The transplant team was consulted soon after birth, and the baby was listed for transplant as soon as the team felt it could safely be done. He’ s currently listed.
“ It’ s really unusual for boys with severe OTC deficiency to survive,” he says.“ And those who do have really bad brain injury. We expect this boy to grow up free of injury from high ammonia.”
Better yet, it’ s possible that one day soon a transplant may no longer be necessary. Dr. McCandless’ s team is currently involved in clinical trials for the first gene therapy for the condition. •
SHAWN MCCANDLESS, MD
Chair, Genetics and Inherited Metabolic Diseases, Children’ s Hospital Colorado
Professor, Pediatrics-Clinical Genetics and Metabolism, University of Colorado School of Medicine
Feb 2021- present Constant monitoring of ammonia levels
Feb 2021: Treatment with oral glycerol phenylbutyrate begins days later
May 2021: Baby is listed for transplant
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